1. Technical Field
The present invention relates to a spindle motor.
2. Description of the Related Art
Generally, in a spindle motor used as a driving device of a recording disk such as a hard disk, or the like, lubricating fluid such as oil, or the like, stored in a gap between a rotating shaft and a sleeve during rotation of the motor and a hydrodynamic bearing using dynamic pressure generated by the lubricating fluid have been variously used.
In addition, as the spindle motor has been used for various portable products such as a net-book, a mobile communication terminal, a game machine, an MP3 player, or the like, it has been improved so as to be appropriate for miniaturization, long-term use, and the like. Particularly, as the spindle motor has been used in the mobile communication terminal, power consumption saving, excellent vibration and noise characteristics, and the like, have been required. However, assembling accuracy is reduced due to a coupling structure of a magnet and a hub, a torque coefficient is reduced due to loss of magnetic flux, and noise and vibration characteristics are deteriorated.
More specifically, FIG. 1 is a schematic cross-sectional view of the spindle motor according to the prior art. As shown in FIG. 1, a spindle motor 100 includes a rotating shaft 110, a hub 120, a sleeve 130, an armature 140, a magnet 150, and a bracket 160.
The sleeve 130 is fixed to the bracket 160, and rotatably supports the rotating shaft 110.
In addition, the hub 120 is coupled to the rotating shaft 110, and has the magnet 150 fixed to an inner circumferential surface thereof.
Further, the bracket 160 has the armature 140 fixed to an outer circumferential portion thereof by press-fitting, adhesion, or the like, and the sleeve 130 fixed to an inner circumferential portion thereof by press-fitting, adhesion, or the like.
However, in a coupling structure of the hub 120 and the magnet 150, an upper end portion of the magnet 150 does not contact a lower end portion of the hub 120 in a direction of the rotating shaft, such that a reference point does not exist during the assembling of the magnet, thereby making it difficult to maintain assembling accuracy.
In addition, as shown in FIG. 2, which is a schematic partial configuration view of the spindle motor according to a second preferred embodiment of the prior art, in a coupling structure of a hub 220 and a magnet 250, the entire upper end portion of the magnet 250 contacts a lower end portion of the hub 220 in a direction of a rotating shaft. Therefore, magnetic flux increases in a direction of the hub 220, such that it is lost, which causes the reduction in a torque coefficient, noise, vibration, or the like.